As a cutting insert for use in a cutting process of a workpiece, for example, cutting inserts disclosed in Japanese Unexamined Patent Publication No. 9-216113 (Patent Document 1) and Japanese Unexamined Patent Publication No. 11-347826 (Patent Document 2) have conventionally been known. The cutting inserts respectively described in Patent Documents 1 and 2 are specifically used in a milling process, such as a face milling process or an end milling process. In the cutting inserts respectively described in Patent Documents 1 and 2, a cutting edge is curved so as to be dented downward in a side view.
In the cutting inserts respectively described in Patent Documents 1 and 2, setting is made so that a cutting edge angle of a major cutting edge with respect to a workpiece is 45° or 90°. Therefore, when cutting the workpiece, a chip thickness increases, thus leading to large impact exerted on the major cutting edge. Furthermore, there occurs a large amount of heat generated when the major cutting edge cuts the workpiece, and there is a large risk that a fracture occurs in the major cutting edge.